Wowser! That Anker looks good value. I've got a 7000maAh Tecknet which weighs 178g which will charge an iPhone approx 4 times., £17.97 on Amazon.

A few years ago I did use a solar charger on the Challenge but did so because I couldn't get a spare battery for my new, or at least new then, camera and the USB portable battery chargers don't give a high enough voltage to charge the camera battery. The solar charger did work but it's heavy and obviously weather dependent. Now a days there is a far greater choice of portable battery chargers some of which have higher voltage output but personally I find 2 spare batteries for my camera and the charger for my phone is all I need. I keep my phone off when not in use and rarely switch it on to use the GPS function.

Ian , i may have been with you out of Loch Ness over East when you corrected me with your rechargeable kit into the upper river system for the Monadhliath . I thought it superb and am only now admitting WEIGHT is a significant factor . thanks bill h.

Hi
I recently bought an Anker Astro 6000mAh from Amazon for £26 for use on the event. Last week I charged 2 Android phones and an iphone 5s and it still had some juice left in it. Weight 132g.